Though this way it made me relate him to Makuta (later known as Teridax) in that he was like a force of nature.

He reminded me more of Sauron from Lord of the Rings, in that what personality he might have once had had been replaced solely by evil and the desire for power for power's sake.

Also, his best moments weren't actions actually performed by him so much as the actions he had already taken prior to the story. The traps he laid were exceedingly cunning (for instance, the way he made it so that his dark magic was the only way to reveal the path to the Crystal Heart, but that assuming that it would get you all the way to the Heart would activate the trap in that door). It shouldn't be ignored that while he's not the most characterized villain we've had, he was definitely the most effective.

The problem was that his effectiveness was really only implied; that backstory that you were talking about wasn't really actually stated, and all that he did that was actually shown was shapeshifting into a cloud and advancing on the tower.

Compared to the other villains, he barely did anything; NMM, even not counting what she did in the intro to the episode, was actively trying to stop the Mane 6, and if nothing else had a better character design. Discord transformed Ponyville into... whatever that was, in the time it took the Mane 6 to get from Canterlot back to Ponyville, and ripped them apart friendship-wise. Chrysalis invaded freaking Canterlot, took out Celestia, and nearly won.

And at the very least, all three of them had decent lines; heck, even Trixie and the Diamond Dogs were better antagonists because of that.